1. Field of the Invention
The invention concerns the encoding of recording cassettes to permit a sensing mechanism on a recorder to identify certain characteristics of each cassette.
2. Description of the Related Art
Specifications are being promulgated by Society of Motion Picture and Television Engineers for a digital videocassette that is being developed internationally. The specifications call for four passages or "coding holes" in an area between curved walls that form part of the enclosure for the tape reels. Each of the coding holes can be either blocked or unblocked, thus permitting a sensing mechanism on the recorder to determine key characteristics of the magnetic recording tape housed in the cassette. The four coding holes allow for sixteen differences in the magnetic recording tape. Differences currently contemplated for encoding include the thickness of the magnetic recording tape and the type of magnetizable material in the tape.
In digital videocassettes that have been publically shown, the coding holes are initially blocked by breakaway tabs molded into the base or body of the cassette. After selected tabs have been broken out, the cassette can no longer be used with a different magnetic recording tape. If the tabs are not broken away until the cassette has been assembled, there is a danger that a tab might become lodged in the cassette and later come loose to damage either the cassette or a recorder.
Digital videocassettes that have been made in accordance with the aforementioned specifications can be used for recording digital data, and in such use it may be desired to use the coding holes for any of a number of purposes, e.g, to allow a recorder to identify the use to which the cassette has been put.
If the body of a cassette is encoded during assembly, a station to do so must be added to the assembly line, and if a mistake is made in the encoding, the miscoded cassettes might need to be destroyed. If there is a need to change the type of tape during production and hence to change the encoding, the line must be stopped until this is done.